IR ablateable driographic printing plates and methods for making same

ABSTRACT

There is disclosed an IR ablateable driographic printing plate (10) including a substrate (12), an IR absorbing layer (14) comprised substantially of a first water based emulsion and a top IR ablatable layer (16) comprised substantially of a second water based emulsion. The term water based is used herein to indicate the precursor materials from which each layer is being deposited are dissolvable in water and not in an organic solvent or solvents.

FIELD OF THE INVENTION

The present invention relates to Infra Red (IR) ablateable driographicprinting plates generally, and more particularly to IR ablateabledriographic printing plates comprised of water based coating layers andmethods for producing same.

BACKGROUND OF THE INVENTION

IR ablateable waterless offset printing plates, also termed IRablateable driographic printing plates, are well known in the art. Theytypically include, in order, a substrate, e.g. a polyester film, anintermediate oleophilic Infra Red (IR) radiation absorbing layer and atop oleophobic layer.

Offset printing plates, including waterless offset printing plates areselectively exposed to radiation in order to expose a latent imagethereon, the image subsequently is selectively colored during printingwith oil based inks, typically the four process inks Cyan, Magenta,Yellow and Black (CMYK) inks.

In most IR sensitive driographic plates, the latent image is recorded byablating the top oleophobic layer and therefore during printing, the oilbased inks are repelled by the areas of the top oleophobic layer whichhave not been ablated during imaging and are not repelled by theoleophilic absorption layer and the substrate revealed in the ablatedareas.

Typically, the top ablateable oleophobic layer is composed of silicone(polysiloxane) or a mixture of silicones cross-linked by cross-linkingagents deposited on the plate from a solution dissolved in an organicsolvent.

For example, naphtha was described as the solvent employed for producingthe top ablateable oleophobic layer using one silicone composition inU.S. Pat. No. 5,378,580 to Leenders and using a mixture of siliconesolutions with cross linking agents in U.S. Pat. No. 5,310,869 to Lewiset al.

In the prior art, the IR absorption layer of driographic printing plateshave been also produced employing organic solvents. For example,published PCT application GB93/01413 to Gutes et al describes the use ofa water-alcohol mixture, for producing the IR absorption layer.

Generally speaking, since organic solvents are used in preparing priorart driographic printing plates, the plates are not environmentallyfriendly.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a waterless Infra Red(IR) ablateable offset printing plate which is produced substantiallywithout using organic solvents.

According to a preferred embodiment of the present invention, the plateis comprised from a substrate coated, in order, by two layers, a waterbased oleophilic IR absorption layer and a water based IR ablateableoleophobic layer.

According to a second preferred embodiment of the present invention, theplate includes a substrate coated, in order, by three layers, a waterbased adhesion promoting layer, a water based IR oleophilic layer and awater based IR ablateable oleophobic layer.

The term water based is used herein to indicate that the precursorsmaterials from which each layer is being deposited are dissolved inwater and not in an organic solvent or solvents.

According to one aspect of the present invention, water is employed withsilicone emulsions and cross-linking agents to produce the topoleophobic layer.

An emulsion as used herein refers to a water insoluble resinsubstantially homogeneously dispersed in water.

According to another aspect of the present invention, water is employedwith suitable resins and suitable IR absorbing materials to produce theIR absorbing oleophilic layer.

According to a further aspect of the present invention, water isemployed with suitable resins to produce the adhesion promoting layer.

An advantage of the plates of the present invention is that they arewater based and therefore, they are more environmentally friendly thanprior art IR ablateable driographic plates.

There is thus provided, according to a preferred embodiment of thepresent invention, an IR ablateable driographic printing platecomprising, in order a substrate, an IR absorbing layer comprisedsubstantially of a first water based emulsion, and a top IR ablateablelayer comprised substantially of a second water based emulsion.

Further, according to a preferred embodiment of the present invention,the plate may also include an adhesion promoting layer between thesubstrate and the IR absorbing layer, the adhesion promoting layer iscomprised substantially from a third water based emulsion.

According to a preferred embodiment of the present invention, the firstwater based emulsion is selected from the group consisting of acrylicemulsions, urethane emulsions, vinylidene chloride emulsions andpolyester emulsions.

Further, the second water based emulsion is selected from the groupconsisting of silicone emulsions and a mixture of silicone emulsions anda cross linking reagent.

Still further, the third water based emulsion is comprised substantiallyfrom aliphatic aqueous colloidal solution dispersion of a urethanepolymer.

Preferably, the thickness of each of the adhesion promoting layer, IRabsorbing layer and the IR ablateable layer ranges between 0.5 and 5grams per square meter.

According to a preferred embodiment of the present invention, the IRablateable layer is oleophobic, the adhesion promoting layer, the IRabsorbing layer and the substrate are oleophilic and the substrate isselected from the group consisting of polyester, aluminum, polyamide andpolycarbonate.

There is also provided, according to a preferred embodiment of thepresent invention, an IR ablateable driographic printing platecomprising, in order, a substrate, an IR absorbing layer and a top IRablateable layer, the improvement comprising a top IR ablateable layercomprised substantially of a water based emulsion. The water basedemulsion is preferably selected from the group consisting of siliconeemulsions and a mixture of silicone emulsions and a cross linkingreagent.

There is also provided, according to a preferred embodiment of thepresent invention, an IR ablateable driographic printing platecomprising a substrate, an IR absorbing layer and a top IR ablateablelayer, the improvement comprising an IR absorbing layer comprisedsubstantially of a water based resin.

Further, the plate may include an adhesion promoting layer between thesubstrate and the IR absorbing layer, the adhesion promoting layer iscomprised substantially from a water based emulsion. Preferably, the IRabsorbing emulsion is selected from the group consisting of acrylicemulsions, urethane emulsions, vinylidene chloride emulsions andpolyester emulsions.

Finally, there is also provided, according to a preferred method of thepresent invention, a method for producing an IR ablateable driographicprinting plate comprising, in order, the steps of coating a substratewith a first water based emulsion, drying the first water basedemulsion, whereby an IR absorbing layer over the substrate is obtained,coating the IR absorbing layer with a second water based emulsion anddrying the second emulsion whereby an IR ablateable layer over the IRabsorbing layer is obtained. The method may also include the step ofcoating the substrate with a water based adhesion promoting emulsion anddrying it before the coating and drying of the IR absorbing layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully fromthe following detailed description taken in conjunction with thedrawings in which:

FIG. 1 is a schematic cross section illustration of a driographic offsetprinting plate, constructed according to a preferred embodiment of thepresent invention; and

FIG. 2 is a schematic cross section illustration of a driographic offsetprinting plate, constructed according to a second preferred embodimentof the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference is now made to FIGS. 1 and 2 which illustrate a three layerdriographic offset printing plate and a four layer driographic offsetprinting plate respectively, constructed according to two preferredembodiments of the present invention.

The plate of FIG. 1, generally referenced 10, comprises a substrate 12,such as a polyester film, an IR absorbing layer 14 and a top IRablateable oleophobic layer 16.

The plate of FIG. 2, generally referenced 20, comprises a substrate 22,an adhesion promoting layer 24 coated thereon, an IR absorbing layer 26and a top IR ablateable oleophobic layer 28.

According to the present invention, water and not an organic solvent isemployed in the production of the IR absorbing layer 14 and the IRablateable oleophobic layer 16 of the plate 10 as well as the adhesionpromoting layer 24, the IR absorbing layer 26 and the top ablateableoleophobic layer 28.

According to a preferred embodiment of the present invention, the topoleophobic layers 16 (FIG. 1) and 28 (FIG. 2) are composed from anaqueous emulsion of silicones mixed with suitable cross-linkingreagents. Examples of suitable aqueous silicone emulsions may beprepared from the following resins: VP 4350 which is a methyl siliconeemulsion, VP 4302 which is a medium hard methyl-phenyl silicone resinand Dehesive 410E, all commercially available from Wacker Silicones ofAdrian Mich., U.S.A, Silikophen; P40/W which is a phenyl methylpolysiloxane, commercially available from Tego Chemie Service Hopewell,Va., U.S.A.; R20-UCC, commercially available from Union Carbide ofDanbury, Conn., U.S.A.; Syloff 22 and Syloff 1170, commerciallyavailable from Dow Corning of Midland, Mich., U.S.A.; SM2013 and SM 30XXcommercially available form General Electric of Waterford, N.Y., U.S.A;and the PCXY silicone emulsion, commercially available from RhonePoulenc of Louisville, Ky., U.S.A.

It will be appreciated that all the silicone emulsions described aboveare sold together with a suitable cross linking reagent or reagents.

According to another preferred embodiment of the present invention, theemulsion may also contain adhesion promoters, surfactants and smallamounts of compatible resins or resin salts.

A preferred method for producing the top oleophobic ablateable layerincludes the following steps:

A. mixing the silicone emulsion or emulsions with the correspondingcross-linking reagent or reagents; and

B. Depositing and drying the mixture over a film to provide a coatinghaving a thickness of between 0.5 and 5 grams per square meter (g.m.s.),a preferred range for employing the coated layer as an IR ablateableoleophobic layer for a driographic plate.

According to a preferred embodiment of the present invention, the IRabsorbing layer 14 (FIG. 1) and 26 (FIG. 2) is comprised of any suitablewater based emulsion prepared from resins selected from the group whichincludes acrylic resins, urethane resins, vinylidene chloride resins andpolyester resins.

Examples of suitable acrylic resins are the Rhoplex B-60A, ACW8-6 andTAW4-11, commercially available from Dock Resins of Binder, N.J., U.S.A,Joncryl 77 and Hydro-Rez 2000, commercially available from LawterInternational, Northbrook, Ill., U.S.A.

Examples of suitable urethane resins are the Bayhydrols B-130, 110, 121,123 and 140AQ, commercially available from Miles of Pitsburg, Pa.,U.S.A; Witcobond W-160, commercially available from Witco of Greenwich,Conn., U.S.A.; and Neorez R-9679 and Neorez 9699, commercially availablefrom Zeneca of Wilmington, Mass., U.S.A.

Examples of suitable vinylidene chloride resins are the Serfene 2011 and2018, commercially available from Morton International, Riverside Plaza,Chicago, Ill., U.S.A.

Examples of suitable polyester resins are the Eastman AQ 29Dcommercially available from Eastman Chemical Co. of Kingsport, Tenn.,U.S.A., Hydro-Rez 100, commercially available form Lawter and Mirasol,and the 10-A-1516, commercially available from Osborn Mercantile ofN.J., U.S.A.

The preferred method for producing the IR absorption layer includes thefollowing steps:

Depositing a suitable water based resin emulsion directly on thesubstrate 12 (FIG. 1) or on the adhesion promoting layer 24 (FIG. 2);and

drying the deposited resin to obtain the desired coated layer.

According to a preferred embodiment of the present invention, theadhesion promoting layer 24 is comprised from an aliphatic aqueouscolloidal solution dispersion of urethane polymer, cross-linked toinsolubilise it. Such a resin solution can be loaded with infra-redabsorbing materials and used in the infra-red absorbing under-layer aswell.

The preferred method for producing the adhesion promoting layer includesthe following steps:

A. Depositing a suitable water based resin on the substrate 22; anddrying the deposited layer to obtain the adhesion promoting coating.

The following examples describe by way of example certain aspects of thepresent invention without limiting its scope.

EXAMPLE I

This is an example illustrating the production of the plate 10.

The IR absorbing layer 14 was produced employing the followingcompositions:

The Neorez R-9679 (marketed by Zeneca Resins of Wilmington, Mass.), isan aliphatic aqueous colloidal dispersion of a urethane polymer--totalsolids by weight of 37%. Stantone 90WD01 is 32% carbon dispersed in anacrylic/water binder total solids approximately 45%. 100 parts by weightof Stantone 90WD01 was mixed with 50 parts by weight of Neorez 9679 andcoated to a weight of 4.2 g.s.m. onto 125 micron polyester film anddried in an oven at 120° C. This yielded the IR absorbing coat 14 coatedon a polyester substrate 12.

The ablateable oleophilic layer 16 was produced as follows:

76 RES 6038 is an aqueous solution of sodium polyacrylate with a totalsolids of 13.5%. This was diluted 1:1 with water and used in thefollowing formulation (all parts in all the examples are by weight):

    ______________________________________                                        Wacker Dehesive 410E 10        parts                                            Water 154 parts                                                               Crosslinker V-20 (Wacker) 1.5 parts                                           Diluted 6038 3 parts                                                          Adhesive Promoter HF-86 (Wacker) 1.5 parts                                    Q2-5211 Super wetting agent                                                   (Dow Corning) 1.8 parts                                                     ______________________________________                                    

This was coated onto the IR absorbing layer 14 produced as describedabove to a thickness of 0.75 grams per square meter and dried in an ovenat 120° C.

The resulting infra-red sensitive printing blank was imaged on anexternal drum system using a half a watt laser diode emitting at 870nano meters. The resulting image was wiped with a dry cloth and theplate printed with Novaless SL 210 waterless ink marketed by K+E (BASF,Stuttgart, Germany). It gave clean background and sharp print. Thisimaging device was used in all the examples.

EXAMPLE II

This is an example illustrating the production of the plate 20.

The adhesion promoting layer 24 was produced as follows:

50 parts of Neorez 9679 were mixed with 1.1 parts of cross-linkerCX-100, 2.5 parts of Ektasolve EP and 50 parts of water. This solutionwas coated to a weight of 1 g.s.m. onto a 120 g.s.m. polyester film 22and dried in an oven at 120° C.

The IR absorbing layer 26 was produced employing the followingcompositions:

150 parts by weight of Stantone 90WD01 were mixed with 50 parts byweight of Rhoplex-60 and coated to a coating weight of 1.2 g.s.m. ontothe adhesive promoting layer 22.

The same top layer of Example I was then coated to a weight of 2 g.s.m.to provide the top oleophobic IR ablateable layer 28.

The resulting blank was imaged and printed as in Example I givingprinted impressions with clean background and sharp print.

EXAMPLE III

The adhesion promoting layer 24 and the IR absorbing layer 26 of ExampleII were used with the following top layer coat to provide an alternativeexample of the plate 20:

    ______________________________________                                        PC-107 (Rhone Poulenc polymer)                                                                     100 parts                                                  PC-95 (Rhone Poulenc cross-linker  10 parts                                   Water 500 parts                                                             ______________________________________                                    

This coating was applied to a weight of 1.8 g.s.m. and dried at 120° C.

for 4 minutes. As in the previous Examples, the printing performanceachieved was good.

EXAMPLE IV

This example illustrates yet another non limiting example of the plate20.

The adhesive layer 24 was produced as follows:

50 parts of Jonacryl 77 (acrylic emulsion) were diluted with 60 parts ofwater and 1.9 parts of Cymel 373 and 2.5 parts of Ektasolve EP added.The emulsion was baconto 175 g.m. polyester film 22 to a weight of 2g.s.m. and dried for 1 minute at 120° C.

The adhesion promoting layer 24 was then over coated with a 2 g.s.m.layer of an infra red absorbing dried film 26 deposited from an emulsionof the following formulation:

    ______________________________________                                        Serfene 2011     50 parts                                                       StanTone 90WD01 120 parts                                                     Water 15 parts                                                              ______________________________________                                    

This layer was also oven dried under the same conditions as the adhesionpromoting layer.

The emulsion used for the IR ablateable oleophobic layer 28 used in thisexample was of the following composition:

    ______________________________________                                        Syloff 7900 (polymer)                                                                            10 parts                                                     Syloff 7922 (cross-linker) 10 parts                                           Water 100 parts                                                             ______________________________________                                    

The coating weight was 2.5. g.s.m. and the resulting plate provided goodimaging qualities.

It will be appreciated that the preferred embodiments describedhereinabove are described by way of example only and that numerousmodifications thereto, all of which fall within the scope of the presentinvention, exist. For example, while the invention is described withrespect to a polyester substrate, any other suitable substrate, such asaluminum, polyamide and polycarbonate plates may be employed.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed hereinabove. Rather, the scope of the present invention isdefined only by the claims that follow:

I claim:
 1. An IR ablateable driographic printing plate comprising:asubstrate; an IR absorbing layer over said substrate, said IR absorbinglayer comprised substantially of a first water based emulsion; and a IRablateable layer over said IR absorbing layer, said IR ablatable layercomprised substantially of a second water based emulsion.
 2. A plateaccording to claim 1 and also comprising an adhesion promoting layerbetween said substrate and said IR absorbing layer, said adhesionpromoting layer is comprised substantially from a third water basedemulsion.
 3. A plate according to any of claims 1 or 2 wherein saidfirst water based emulsion is selected from the group consisting ofacrylic emulsions, urethane emulsions, vinylidene chloride emulsions andpolyester emulsions.
 4. A plate according to claim 1, wherein saidsecond water based emulsion is selected from the group consistingof:silicone emulsions, and a mixture of silicon emulsions and a crosslinking reagent.
 5. A plate according to claim 2 wherein said thirdwater based emulsion is comprised substantially from aliphatic aqueouscolloidal solution dispersion of a urethane polymer.
 6. A plateaccording to claim 2 wherein the thickness of each of said adhesionpromoting layer, IR absorbing layer and said IR ablateable layer rangesbetween 0.5 and 5 grams per square meter.
 7. A plate according to claim1 wherein said IR ablateable layer is oleophobic.
 8. A plate accordingto claim 2 wherein said adhesion promoting layer, said IR absorbinglayer and said substrate are oleophilic.
 9. A plate according to claim 1wherein said substrate is selected from the group consisting ofpolyester, aluminum, polyamide and polycarbonate.
 10. In an IRablateable driographic printing plate comprising, in order, a substrate,an IR absorbing layer and a top IR ablateable layer, the improvementcomprising a top IR ablateable layer comprised substantially of a waterbased emulsion.
 11. In a plate as in claim 10 wherein said water basedemulsion is selected from the group consisting of silicone emulsions anda mixture of silicone emulsions and a cross linking reagent.
 12. Amethod for producing an IR ablateable driographic printing platecomprising, in order:coating a substrate with a first water basedemulsion; drying said first water based emulsion, whereby an IRabsorbing layer over said substrate is obtained; coating said IRabsorbing layer with a second water based emulsion; and drying saidsecond emulsion whereby an IR ablateable layer over said IR absorbinglayer is obtained.
 13. A method according to claim 12, furthercomprising coating said substrate with a water based adhesion promotingemulsion and drying it before said coating and of drying said IRabsorbing layer.